(function() {
    class Animal {
        name:string;
        constructor(name:string) {
            this.name = name;
        }
        say() {
            console.log(`我是一只${this.name}`);
        }
    }
    class Cat extends Animal {
        age:number;
        constructor(name:string,age:number) {
            super(name)
            this.age = age
        }
    }
    let cat1 = new Cat('小猫',3)
    console.log(cat1);
    cat1.say();
})()